throw new Exception("The method or operation is not implemented.");

            // Frequently used exception samples, Don't Remove.
            //throw new ApplicationException("message");
            //throw new ArgumentException 
            //throw new ArgumentNullException
            //throw new ArithmeticException 
            //throw new FormatException 
            //throw new IndexOutOfRangeException 
            //throw new InvalidOperationException 
            //throw new KeyNotFoundException 
            //throw new MissingFieldException 
            //throw new NotImplementedException 
            //throw new NotSupportedException 
            //throw new NullReferenceException 
            //throw new OperationCanceledException 
            //throw new PlatformNotSupportedException 
            //throw new RankException 
            //throw new TimeoutException 
            //throw new UnauthorizedAccessException 
----------
// throw example
using System;
public class ThrowTest 
{
    static void Main() 
    {
        string s = null;

        if (s == null) 
        {
            throw new ArgumentNullException();
        }

        Console.Write("The string s is null"); // not executed
    }
}

----------

using System;
using System.IO;
public class ProcessFile
{
   public static void Main()
      {
      FileStream fs = null;
         try
            //Opens a text tile.
            {
            fs = new FileStream("data.txt", FileMode.Open);
            StreamReader sr = new StreamReader(fs);
            string line;
            //A value is read from the file and output to the console.
            line = sr.ReadLine();
            Console.WriteLine(line);
            }
         catch(FileNotFoundException e)
            {
            Console.WriteLine("[Data File Missing] {0}", e);
            throw new FileNotFoundException("[data.txt not in c:\\dev directory]",e);
            }
         finally
            {
            fs.Close();
            }
      }
}